Have a problem with my 07 Rhino 450. Sometimes when I let off the accelerator to bring the engine to idle, the engine speed does not decrease enough to shift gears. The rpm stays a little too high like the throttle is sticking. I can rev the engine and let off the accelerator quickly, but it doesn't help. The only way I can get the engine slow enough to shift gears is to choke it just a little. Once the engine slows enough to shift gears and I let the choke off, the engine will idle at the proper speed. Any one have any ideas about what is going on?